Application And Preparation Of Polymer Emulsion For Cement-based Waterproof Material

Concrete is a widely used building material,but cracking and leakage of concrete have always been big problems that plague the quality of cement concrete buildings.Cement modified by polymer can effectively solve the problem of cement application.The polymer varieties used to modify cement concrete mainly include water-based polymers,liquid resins and polymer emulsions.The acrylate polymer emulsion for cement-based waterproofing materials is a green material with good crack resistance,high film formation density and good water-blocking effect,and these merits make up for the lack of flexibility of cement-based materials and defects of poor aging resistance of polymer materials.With the deepening of research,cement-based waterproofing material polymerization emulsions have been vigorously developed and widely used in many fields.Firstly,a polymer emulsion for cement-based waterproofing materials was synthesized.The effect of variables on the properties of polymer emulsions was investigated.The variables include the pre-emulsification process,the amount of seed monomers,the reaction time of the seed monomers,the amount of the emulsifier in the emulsion polymerization,the temperature during the reaction and the rotational speed of the emulsion polymerization paddle.During pre-emulsification process,high rotation speed is beneficial to the emulsification process and the stability of the emulsion.Through experimental analysis,the better rotation speed is between 450-500 rpm.In this range of rotation speed,the obtained pre-emulsion has good quality and good stability.In the process of seed emulsion polymerization,when the amount of monomer is constant,the particle size of the latex particles is inversely proportional to the amount of seed.The particle size and distribution of the latex particles can be controlled by seed emulsion polymerization to prepare polymer emulsion having a small particle size,uniformity and stability.As the rotation speed of the stirring paddle increases,the viscosity of the emulsion decreases.The viscosity of the emulsion is large at the late stage of the reaction.Hence,using 450-500 rpm for the stirring paddle speed is beneficial to mass transfer,heat transfer and the decrease of viscosity of the emulsion.When the reaction temperature increases,the conversion rate of the monomer also increases.The preferred reaction temperature of the experiment is 90 ° C,and the temperature change has a great influence on the product.The synthetic polymer emulsion was used in the preparation of cement-based waterproofing materials.The effects of filming aids,dispersants and plasticizers in polymer cement waterproof coating formulations were investigated.At the same time,the relationship between water absorption,tensile properties,drying time,low temperature flexibility and different liquid to powder ratios of polymer cement waterproof coatings was also discussed.When the ratio of liquid to powder increases,the viscosity of polymer cement waterproof coating significantly decreases and it is helpful to the construction process.But when the viscosity is too low,it is not conducive to the construction of walls and other places.As the ratio of liquid to powder increases,the drying time of the paint film increases and the construction efficiency significantly decreases.When the ratio of liquid to powder increases,the water absorption rate of the polymer cement waterproof coating decreases first and then increases and the water absorption rate of the paint film has a lowest value.The polymer emulsion has a significant improvement effect on the low temperature flexibility and water impermeability of the cement.In general,it is preferable to determine the ratio of liquid to powder to be between 0.6 and 0.8,then we can obtain a cement-based polymer waterproof material excellent in performance.